Sensitization of selenium and iridium emulsions

Abstract

The invention is generally accomplished by a method of sensitizing comprising providing tabular silver bromoiodide grains or bromoiodide grains doped with Se and Iridium bringing said grains into contact with a benzothiazolium salt or hydrolyzed benzothiazolium salt comprising ##STR1## wherein R 1 is hydrogen, alkyl of from 1 to 8 carbon atoms, or aryl of from 6 to 10 carbon atoms, R 4 and R 5 are independently hydrogen or halogen atoms, aliphatic or aromatic hydrocarbon moieties optionally linked through a divalent oxygen or sulfur atom; or cyano, amino, amido, sulfonamido, sulfamoyl, ureido, thioureido, hydroxy, --C(O)M, or --S(0) 2 M groups, wherein M is chosen to complete an aldehyde, ketone, acid, ester, thioester, amide, or salt; Y 1 is a charge balancing counter ion; and Q is a substituent of the formula: --LCONHS0 2 R, --LCONHS0 2 NHCOR alkyl, sulfoalkyl, phosphoalkyl, hydroxyalkyl, or L--CONH 2 wherein L is an alkyl group of from 1 to 8 carbon atoms and R is an alkyl group of from 1 to 8 carbon atoms or a primary amino group, bringing said grains into contact with a mercaptobenzotetrazol comprising ##STR2## wherein R 3 is --CH 2 CONH 2 , --NHCOR 2 , --NHCONHR 2 , --LCONHR 2 , --COOH, --SO 3 , --OH, --SO 2 NH 2 , --SO 2 NHR 2 , halogen, alkyl, alkoxy, or aryloxyl, R 2 is an alkyl with 1-8 carbon or an aryl of 1 to 10 carbons, and heating to complete chemical sensitizing of said grains.

I claim: 
     
       1. A method of sensitizing comprising providing tabular silver bromoiodide grains or silver bromide grains doped with Se and Iridium, bringing said grains into contact with a benzothiazolium salt comprising a 3-methyl-1-3-benzothiazolium salt or a 3-(N-methylsulfonyl) carbamolyethyl benzothiazolium salt, bringing said grains into contact with a mercaptobenzotetrazole in an amount between about 5×10 -6  and 1×10 -4  mole/Ag mole, said mercaptobenzotetrazole comprising ##STR8## wherein R 3  is --CH 2  CONH 2 , --NHCOR 2 , --NHCONHR 2  LCONHR 2 , --COOH, --SO 3 , --OH, --SO 2  NH 2 , --SO 2  NHR 2 , halogen, alkyl, hydrogen, alkoxy, or aryloxyl, L is an alkyl group of from 1 to 8 carbon atoms,   R 2  is an alkyl with 1-8 carbon or an aryl of 6-10 carbon atoms,   and heating to complete chemical sensitizing of said grains with the proviso that said benzothiazole and said mercaptobenzotetrazole compound C are added prior to said heating to complete chemical sensitizing.   
     
     
       2. The method of claim 1 wherein sulfur and gold containing chemical sensitizers are added to said emulsion prior to said heating. 
     
     
       3. The method of claim 2 wherein spectral sensitizers are also added prior to heating. 
     
     
       4. The method of claim 1 wherein said benzothiazolium salt is added in an amount between 1×10 -6  and 1×10 -3  mole/Ag mole. 
     
     
       5. The method as in claim 1 wherein the emulsion is a bromoiodide emulsion with I content from 0.1 to 12%. 
     
     
       6. The method of claim 1 wherein said silver bromoiodide grains have an average aspect ratio of greater than 2. 
     
     
       7. The method of claim 6 wherein said grains have an aspect ratio of greater than 5. 
     
     
       8. The method of claim 1 wherein said selenium is present in an amount between about 1×10 4  and 1×10 -8  mole/Ag mole and said Iridium is present in an amount between about 1×10 -5  and 1×10 -9  mole/Ag mole. 
     
     
       9. The method of claim 8 wherein said Iridium is present in an amount between 1×10 -6  and 1×10 -8  mole/Ag mole and said selenium is present in an amount between 1×10 -5  and 1×10 -7  mole/Ag mole. 
     
     
       10. The method of claim 1 wherein said grains comprise 0.1 to 15 percent iodide. 
     
     
       11. The method of claim 1 wherein said mercaptobenzotetrazole comprises 1-(3-acetamido-phenyl)-5-mercaptotetrazole. 
     
     
       12. The method of claim 1 wherein said mercaptobenzotetrazole comprises 1-phenyl-5-mercaptotetrazole. 
     
     
       13. The method of claim 1 wherein said benzothiazolium salt comprises a 3-methyl-1-3-benzothiazolium salt or a 3-(N-methylsulfonyl) carbamoylethyl benzothiazolium salt.